Antineutrino Interactions Research Articles

A determination of? s from the transverse momenta of hadrons produced in neutrino and antineutrino interactions

TheW andQ2 dependence of the transverse momentum of the forward-going hadrons in deep inelastic neutrino charged current interactions on neon is studied. The data were obtained by exposing BEBC filled with a Ne/H2 mixture to the CERN SPS wide-band neutrino beam. The data on average transverse momentum are compared to a model which includes first order QCD, intrinsic quark momentum in the nucleon and Fermi motion, as well as a simple model for hadronization. The model is found to describe the data well. Values of αs=0.16±0.02(stat)±0.02(syst.)±0.03(frag.) at an averageQ2 of 15.4±0.4 GeV2/c2 and\(\Lambda _{\overline {MS} } = 216_{ - 99}^{ + 113} \) (stat.)−90+100 (syst.)−90+130, (frag.) MeV/v for three flavours are extracted.

Coherent production ofa 1 ? mesons and (??)? systems by antineutrinos on neon

The coherent production of 3π systems by charged current antineutrino interactions on neon nuclei is studied in the bubble chamber BEBC exposed to the CERN SPS wide band beam. The coherent signal is attributed mainly to (ρπ) production, where the (ρπ) system is either non-resonant or comes from the decay ofa1 mesons. The kinematical variables and the total cross section are compared with the predictions of the meson dominance model.

Results of a search for free quarks with a large avalanche chamber in high-energy neutrino interactions

A search for free quarks liberated via neutrino-quark coupling using the highest possible available energy was performed at CERN (WA-44 experiment) in the neutrino wide-band beam. The neutrino interactions take place in a 23 ton lead target. A forward large avalanche chamber is triggered when one or more charged particles from the neutrino (antineutrino) interactions cross two sets of counter hodoscopes. Ionization measurements in the avalanche chamber have been performed using two measuring machines: HPD in Bologna and PERPR in Frascati. The 6% expected statistical fluctuations in the ionization measurements have been obtained on one metre long tracks. This allowed an accurate analysis of the data to search in the 1/3 and even in the 2/3 charge regions. About 3.7·105 tracks were observed in the chamber, from about 105 neutrino (antineutrino) interactions. The analysis of the digitized data has selected 20 candidates for fractional charges. After a detailed analysis of both pictures and measurements, and a complete investigation of all possible instrumental effects, one event remains as a fractional charge (+1/3) candidate. This candidate has a small probability to be an edge effect in the apparatus. However this event is at the expected level of candidate events from the rejection power of our detector. Upper limits (90% c.l.) on the flux of quarks produced in both neutrino and antineutrino interactions are at the level of a few 10−5.

Investigation of exclusive channels in [formula omitted] charged current interactions

An analysis has been performed of neutrino and antineutrino interactions with protons and neutrons in a deuterium bubble chamber. The interactions under study are quasielastic neutrino-neutron scattering and one-, two- and three-pion production reactions. Results are presented on cross sections, effective mass distributions, resonance production, momentum transfer distributions and coefficients of the decay angular distributions. Where possible, comparisons are made with existing theoretical models and predictions.

Measurement of the inclusive charged-current cross section for neutrino and antineutrino scattering on isoscalar nucleons

This paper reports on measurements of the total cross section for the inclusive reaction vμ+N, as a function of incident energy. Neutrinos and antineutrinos with energy in the range 30–300 GeV were produced in the 1982 Fermilab narrow-band neutrino beamline. A total of 35 000 neutrino and 7000 antineutrino interactions were recorded in the CCFR detector located in LabE. The incident neutrino flux was determined by methods similar to those used in previous experiments. The rate of increase with energy of the total cross section (σ/Ev) in the range 30 to 75 GeV was determined to be 0.659±0.005(stat)±0.039(syst)×10−38 cm2/GeV and 0.307±0.008(stat)±0.020(syst)×10−38 cm2/GeV for incident neutrinos and antineutrinos, respectively. The 5.9% systematic errors are due primarily to uncertainties in the flux intensity measurement. The energy dependence of the cross section in the regionEν=100–300 GeV was found to be linear, as determined by relative normalization techniques. A weighted average of our previous and present measurement for the total ν-N cross section yields: $$\begin{gathered} \sigma (vN) = 0.666 \pm 0.020(statistical \hfill \\ + systematic)E_v 10^{ - 38} cm^2 ; \hfill \\ \sigma (\bar vN) = 0.324 \pm 0.014(statistical \hfill \\ + systematic)E_v 10^{ - 38} cm^2 ; \hfill \\ \end{gathered} $$ .

Cross-section measurements of single pion production in charged current neutrino and antineutrino interactions

All six exclusive single pion production processes from neutrino and antineutrino charged current interactions are studied in the energy range between 3 and 30 GeV. Using a quark model for single pion production from Rein and Sehgal we fitted the aximal mass parameter from total cross sections and compare the results with values from other experiments and the world-averages.

Observation of shadowing of neutrino- and antineutrino-nucleus interactions and comparison with PCAC predictions

Comparing the kinematical distributions of events obtained on neon and deuterium targets in similar experimental conditions reveals a reduction of the neutrino and antineutrino charged current cross section per nucleon in neon at low Q 2. The effect, interpreted as due to geometric shadowing of the weak propagator in interactions of neutrinos and antineutrinos with nuclei, agrees well with predictions derived from PCAC.

Coherent production of pi + and pi - mesons by charged-current interactions of neutrinos and antineutrinos on neon nuclei at the Fermilab Tevatron.

Coherent single-pion production on neon nuclei is studied using the Fermilab 15-ft bubble chamber filled with a heavy Ne-H{sub 2} mixture and exposed to the Tevatron neutrino beam. In the neutrino energy range 40--300 GeV, the net signal is 20{plus minus}6 events, giving a corrected rate per charged-current event of (0.26{plus minus}0.10)%. The cross section and kinematic distributions agree with the predictions of a model based on partial conservation of axial-vector current and meson dominance.

A measurement of the proton structure functions from neutrino-hydrogen and antineutrino-hydrogen charged-current interactions

Within the framework of the quark-parton model, the quark and anti-quark structure functions of the proton have been measured by fitting them to the distributions of the events in the Bjorkeny variable. The data used form the largest sample of neutrino and antineutrino interactions on a pure hydrogen target available, and come from exposures of BEBC to the CERN wide band neutrino and antineutrino beams. It is found that the ratiodv/uv of valence quark distributions falls with increasing Bjorkenx. In the context of the quark-parton model the results constrain the isospin composition of the accompanying diquark system. Models involving scattering from diquarks are in disagreement with the data.

Higher twist and the structure functions F2 and xF3

Results from the BEBC WA59 experiment are presented in which the isoscalar structure functions F 2( x, Q 2) and xF 3( x, Q 2) are measured to low Q 2 and W 2 using neutrino and antineutrino interactions on neon. Possible higher twist contributions to the determination of the QCD parameter Λ are investigated, with the result that a low Λ MS of around 100 MeV and a small negative higher twist effect are found to describe the data adequately.

Experimental limit on the flux of relic antineutrinos from past supernovae.

We report the result of a search in the Kamiokande II detector for the interactions of electron-type antineutrinos in the energy interval 19 to 35 MeV. We measure directly a 90%-confidence-level upper limit of 226 cm/sup -2/ sec/sup -1/ on the flux of electron antineutrinos with energies in that interval. An upper limit on the total flux of relic antineutrinos from past supernovae is obtained as a function of the effective equilibrium temperature of the relic antineutrino sea.

Total cross sections of charged-current neutrino and antineutrino interactions on isoscalar nuclei

New measurements of the total crosssections of charged-current interactions of muonneutrinos and antineutrinos on isoscalar nuclei have been performed. Data were recorded in an exposure of the CHARM detector in an 160 GeV narrow-band beam. The antineutrino flux was determined from the measurements of the pion and kaon flux, and independently from the muon flux measured in the shield; the two methods are found to agree. The neutrino flux was determined from the muon flux ratio forv μ and\(\bar v_\mu \) runs which was normalized to the antineutrino flux. The cross-section slopes thus determined are $$\begin{gathered} \sigma _T^{\bar v} /E = (0.335 \pm 0.004(stat) \hfill \\ \pm 0.010(syst)).10^{ - 38} cm^2 /(GeV \cdot nucleon) \hfill \\ \sigma _T^v /E = (0.686 \pm 0.002(stat) \hfill \\ \pm 0.020(syst)).10^{ - 38} cm^2 /(GeV \cdot nucleon) \hfill \\ \end{gathered} $$ The momentum sum of the quarks in the nucleon and the ratio of sea quark to total quark momentum are derived from the measurements.

A study of the EMC effect using neutrino and antineutrino interactions in neon and deuterium

Nearly 40000 neutrino and antineutrino interactions in BEBC are compared to measure the differences between neon and deuterium in the quark and antiquark distributions and in the nucleon structure functions. The ratio of Ne to D cross sections indicates some decrease betweenx∼0.2 andx∼0.6. They distributions show there is no significant increase in the neon sea, but prefer a small decrease. Taken altogether, thex andy distributions and the measured total cross-sections indicate some change in the shape of the valence distributions. No significant dependence onA is observed for either the shape of the sea or the ratio of longitudinal to transverse cross-sections.

Coherent production ofρ − mesons in charged current antineutrino-neon interactions in BEBC

Coherent production ofρ − mesons in charged current antineutrino interactions on neon nuclei is studied in the BEBC bubble chamber exposed to the CERN SPS wide band beam. The cross section is measured to be (95±25)·10−40 cm2 per neon nucleus, averaged over the beam energy spectrum. The distributions of kinematical variables and the absolute value of the cross section are in agreement with theoretical predictions based on the CVC hypothesis and the vector meson dominance model.

Neutral strange particle exclusive production in charged current high-energy antineutrino interactions

The cross section of the quasi-elastic reactions\(\bar v_\mu p \to \mu ^ + \Lambda (\Sigma ^0 )\) in the energy range 5–100 GeV is determined from Fermilab 15′ bubble chamber antineutrino data. TheQ2 analysis of quasi-elastic Λ events yieldsMA=1.0±0.3 GeV/c2 for the axial mass value. With zero µΛK0 events observed, the 90% confidence level upper limit\(\sigma (\bar v_\mu p \to \mu ^ + \Lambda {\rm K}^0 )< 2.0 \cdot 10^{ - 40} cm^2 \) is obtained. At the same time, we found that the cross section of reaction\(\bar v_\mu p \to \mu ^ + \Lambda {\rm K}^0 + m\pi ^0 \) is equal to\(\left( {3.9\begin{array}{*{20}c} { + 1.6} \\ { - 1.3} \\ \end{array} } \right) \cdot 10^{ - 40} cm^2 \).

Total neutrino and antineutrino charged current cross section measurements in 100, 160, and 200 GeV narrow band beams

Neutrino and antineutrino total charged current cross sections on iron were measured in the 100, 160, and 200 GeV narrow band beams at the CERN SPS in the energy range 10 to 200 GeV. Assuming σ/E to be constant, the values corrected for non-isoscalarity are σv/E = (0.686 ± 0.019) * 10−38 cm2/ (GeV · nucleon) and σv/E = (0.339 ± 0.010) * 10−38 cm2/ (GeV·nucleon). Between 50 and 150 GeV no energy dependence of σ/E was observed within ±3% for neutrino and ±4% for antineutrino interactions.

Spin alignment of ρ 0 mesons produced in antineutrino and neutrino neon charged-current interactions

In a bubble chamber experiment with BEBC the spin alignment parameter η= 1 2 (2ϱ 00 − ϱ 11 − ϱ −1−1) is measured for ϱ 0 mesons produced in deep inelastic charged-current antineutrino and neutrono interactions on neon. In the current fragmentation region η is found to be η v =0.48±0.27 ( stat.)±0.15 ( syst.) for v Ne and η v =0.12±0.20 (stat.)±0.10 (syst.) for vNe interactions

Experimental test of the PCAC-hypothesis in charged current neutrino and antineutrino interactions on protons

Data obtained with the bubble chamber BEBC at CERN are used for the first significant test of Adler's prediction for the neutrino and antineutrino-proton scattering cross sections at vanishing four-momentum transfer squaredQ 2. An Extended Vector Meson Dominance Model (EVDM) is applied to extrapolate Adler's prediction to experimentally accessible values ofQ 2. The data show good agreement with Adler's prediction forQ 2→0 thus confirming the PCAC hypothesis in the kinematical region of high leptonic energy transfer ν>2 GeV. The good agreement of the data with the theoretical predictions also at higherQ 2, where the EVDM terms are dominant, also supports this model. However, an EVDM calculation without PCAC is clearly ruled out by the data.

Measurement of the neutral to charged current cross section ratios for neutrino and and antineutrino interactions on protons

The ratios R vp and R vp of the neutral current to charged current cross sections for neutrino and antineutrino interactions on protons have been measured in BEBC. The beam was the CERN SPS 400 GeV wideband beam. The bubble chamber, equipped with the standard External Muon Identifier, was surrounded with an additional plane of wire chambers (Internal Picket Fence), which was added to improve neutral current event identification. For a total transverse momentum of the charged hadrons above 0.45 GeV/ c and a charged multiplicity of at least 3, it was found that R vp = 0.384 ± 0.015 and R vp = 0.338 ± 0.014 ± 0.016, corresponding to a value of sin 2θ w(M w MS of 0.225 ± 0.030 . Combining the results from hydrogen and an isoscalar target, the differences of the neutral current chiral coupling constants were found to be u 2 l− d 2 L = −0.080 ± 0.043 ± 0.012 and u 2 R− d 2 R = 0.021±0.055±0.028.

Inclusive study of neutrino and antineutrino interactions with nuclei at energies $$E_v^{( - )} \leqq 30$$ GeV

Neutrino and antineutrino charged current reactions are studied inclusively at energies below 30 GeV using the freon filled bubble chamber SKAT at the Serpukhov accelerator. Data are given for the nucleon structure functions and the differential spectradσ/dy. The results are compared with predictions of the Quark-Parton Model and Quantum Chromodynamics.